The volume is designed as a reference work on the Cebidae, third of the three families of living New World monkeys, the other two having been covered in volume 1. All aspects of cebid biology will be treated. Included are keys to the identification of genera, species and subspecies, range maps, gazetteer, complete synonymies, exhaustive bibliographies and illustrations. The research will be based primarily on the taxonomy of each species with emphasis on gross morphology, cytogenetics, zoogeography, behavior and, in general, will elaborate on the groundwork and principles established in volume 1. The order of procedure will give priority to cebids most important in biomedical research with Saimiri and Aotus heading the list. Organization of the volume, however, will be phylogenetic. Discoveries, taxonomic revisions and original observations of immediate interest will be published as preliminary reports.